Circular radiation heat shields with temperature dependent emissivities: transient and steady-state analyses

Resumo

Radiation heat loss is an important type of heat loss in thermal systems. In this work, a numerical study of the transient response of two circular radiation heat shields inserted between two parallel and circular surfaces of emissivities ε₁ and ε₂ is presented. The same dimensions have been assumed for the two main radiating surfaces and the two radiation shields. The radiation shields are assumed to have different emissivities on their top (ε₃ and ε₅) and bottom ( ε₄ and ε₆) surfaces, and both are assumed to be different but linear functions of temperature. A specific configuration is investigated in detail to highlight the transient temperature and heat transfer characteristics of the system. Some new results for the transient temperature and heat transfer characteristics of the system such as the effect of shield location, shield emissivities, the temperature dependence of shield emissivities, system dimensions, temperatures of the hot and cold surfaces and emissivities of the hot and cold surfaces are presented for future references. It has been observed that increasing the temperature of the first radiation shield by changing a parameter such as surface emissivity or distance between the radiation shield or the temperature of the hot surface, will not necessarily decrease the temperature of the second radiation shield.